Slant plate type compressor with variable displacement mechanism

Abstract

A slant plate type compressor with a capacity or displacement adjusting mechanism is disclosed. The compressor includes a housing having a cylinder block provided with a plurality of cylinders and a crank chamber. A piston is slidably fitted within each of the cylinders and is reciprocated by a drive mechanism which includes a slant plate having a surface with an adjustable incline angle. The incline angle is controlled according to the pressure in the crank chamber. The pressure in the crank chamber is controlled by a control mechanism which comprises a first passageway linking the crank chamber and the suction chamber, and a valve device which controls the closing and opening of the first passageway. The valve device includes a valve element which directly controls the closing and opening of the first passageway, a first valve control device which controls the position of the valve element in response to pressure in the crank chamber, and a second valve control device which include a second passageway linking the crank chamber and the discharge chamber and an actuator disposed in the second passageway. The second valve control device controls the predetermined crank pressure operating point of the first valve control device. The operation of the second valve control device is controlled in response to changes in the thermodynamic characteristics of the refrigerant circuit so as to open and close the second passageway.

We claim: 
     
       1. In a slant plate type refrigerant compressor including a compressor housing enclosing a crank chamber, a suction chamber and a discharge chamber therein, said compressor housing comprising a cylinder block having a plurality of cylinders formed therethrough, a piston slidably fitted within each of said cylinders, a drive means coupled to said pistons for reciprocating said pistons within said cylinders, said drive means including a drive shaft rotatably supported in said housing and coupling means for drivingly coupling said drive shaft to said pistons such that rotary motion of said drive shaft is converted into reciprocating motion of said pistons, said coupling means including a slant plate having a surface disposed at an adjustable inclined angle relative to a plane perpendicular to said drive shaft, the inclined angle of said slant plate adjustable to vary the stroke length of said pistons in said cylinders to vary the capacity of the compressor, a passageway formed in said housing and linking said crank chamber and said suction chamber in fluid communication, and capacity control means for varying the capacity of the compressor by adjusting the inclined angle, said capacity control means including a first valve control means and a response pressure adjusting means, said first valve control means for controlling the opening and closing of said passageway in response to changes in refrigerant pressure in said compressor to control the link between said crank and said suction chambers to thereby control the capacity of the compressor, said first valve control means responsive at a predetermined pressure, said response pressure adjusting means for controllably changing the predetermined pressure at which said first valve control means responds, the improvement comprising: said response pressure adjusting means including a hollow portion, a piston element disposed in said hollow portion and dividing said hollow portion into a first space open to said discharge chamber and a second space isolated from said discharge chamber, said first and second spaces linked by a gap between the inner surface of said hollow portion and an outer surface of said piston element, said piston element linked to said first valve control means, a communicating path linking said second space with said crank chamber, and a second valve control means for controlling the link of said second space to said crank chamber, said second valve control means functioning in response to an external signal to vary the pressure in said second space between the discharge pressure and the crank pressure.   
     
     
       2. The compressor recited in claim 1, said piston element disposed adjacent an actuating rod, said actuating rod linked to said first valve control means by a first elastic element. 
     
     
       3. The compressor recited in claim 2, said second valve control means comprising a solenoid actuator. 
     
     
       4. The compressor recited in claim 2, further comprising a second elastic element, said second elastic element disposed in said second space and biasing said piston element towards said actuating rod. 
     
     
       5. The compressor recited in claim 2, said first valve control means comprising a longitudinally expanding and contracting bellows and a valve element attached at one end of said bellows, said actuating rod having one end disposed adjacent said piston element. 
     
     
       6. The compressor recited in claim 5, further comprising a second elastic element, said second elastic element disposed in said second space and biasing said piston element towards said actuating rod. 
     
     
       7. The compressor recited in claim 1, said response pressure adjusting means further comprising a second hollow portion linked by a channel to said second space of said first hollow portion, said second hollow portion linked to said crank chamber, and a solenoid actuator disposed in said second hollow portion, said solenoid actuator controlling the opening and closing of said channel to control the link of said second space and said crank chamber in response to an external signal. 
     
     
       8. The compressor recited in claim 1, said compressor forming part of a refrigeration circuit, said response pressure adjusting means responding to a thermodynamic characteristic of the refrigeration circuit. 
     
     
       9. The compressor recited in claim 8, the refrigeration circuit comprising an evaporator, wherein the thermodynamic characteristic is the temperature of the air passing through and exiting the evaporator. 
     
     
       10. The compressor recited in claim 8, the refrigeration circuit comprising an evaporator, wherein the thermodynamic characteristic is the pressure of the refrigerant exiting the evaporator. 
     
     
       11. The compressor recited in claim 1, said first valve control means responsive to the suction chamber pressure. 
     
     
       12. The compressor recited in claim 1, said first valve control means responsive to the crank chamber pressure. 
     
     
       13. In a slant plate type refrigerant compressor including a compressor housing enclosing a crank chamber, a suction chamber and a discharge chamber therein, said compressor housing comprising a cylinder block having a plurality of cylinders formed therethrough, a piston slidably fitted within each of said cylinders, a drive means coupled to said pistons for reciprocating said pistons within said cylinders, said drive means including a drive shaft rotatably supported in said housing and coupling means for drivingly coupling said drive shaft to said pistons such that rotary motion of said drive shaft is converted into reciprocating motion of said pistons, said coupling means including a slant plate having a surface disposed at an adjustable inclined angle relative to a plane perpendicular to said drive shaft, the inclined angle of said slant plate adjustable to vary the stroke length of said pistons in said cylinders to vary the capacity of the compressor, a passageway formed in said housing and linking said crank chamber and said suction chamber in fluid communication, and capacity control means for varying the capacity of the compressor by adjusting the inclined angle, said capacity control means including a valve control means and a response pressure adjusting means, said valve control means for controlling the opening and closing of said passageway in response to changes in refrigerant pressure in said compressor to control the link between said crank and said suction chambers to thereby control the capacity of the compressor, said valve control means responsive at a predetermined pressure, said response pressure adjusting means for controllably changing the predetermined pressure at which said first valve control means responds, the improvement comprising: said response pressure adjusting means including a moveable element linked to said valve control means, said moveable element moving in response to a comparison of the pressure on the opposite sides thereof, one side of said moveable element linked in fluid communication with said crank chamber, and pressure control means for controlling the pressure on said one side of said moveable element by controlling the link of said one side with said crank chamber, said pressure control means responsive to an external signal.   
     
     
       14. The compressor recited in claim 13, said one side of said moveable element linked in fluid communication with said crank chamber by a conduit, said pressure control means controlling the opening and closing of said conduit in response to the external signal. 
     
     
       15. The comprssor recited in claim 14, the opposite side of said moveable element linked to said valve control means by an elastic element, the opposite side also linked in fluid communication with said discharge chamber. 
     
     
       16. The compressor recited in claim 13, said valve control means responsive to the suction pressure. 
     
     
       17. The compressor recited in claim 13, said valve control means responsive to the crank pressure.